Certain types of optical fiber cables carry optical fibers in fiber bundles, with each fiber bundle carrying one or more optical fibers, typically between one and twelve optical fibers. The fiber bundles typically have a select order, which in one case is defined by a color code based on industry standards. In such cables, the fiber bundles can either be fixed relative to one another (i.e., “fixed tube”), such as in a ribbon cable or can be loose, i.e., free to move relative to one another (i.e., “loose tube”). An optical fiber cable can thus be referred to either as a fixed-tube cable or a loose-tube cable.
It is known in the art that a fixed-tube cable, and especially a fixed-tube ribbon cable, is difficult to route through an infrastructure (e.g., a data center, a control room, a wiring closet, etc.) because it bends with difficulty in the plane of the fiber bundles. Because the number of turns and twists for a given route are not known beforehand, the ribbon cable may need to bend in both the easy and the difficult directions, with the latter possibly leading to undesirable and uncontrolled mechanical and optical loss effects during installation. On the other hand, an advantage of a ribbon cable is that the bundles maintain their relative positions over the length of the cable, which allows for the ends of the fiber bundles and the optical fibers therein to be processed (e.g., handled, spliced and connectorized) all at once, i.e., in one step. This one-step process is simple and results in a substantial time savings in the installation process.
In contrast, a loose-tube cable is relatively easy to route because the bending stresses are the same in every direction. Further, the fiber bundles can shift slightly in both the longitudinal and lateral directions to minimize the overall strain associated with each individual fiber. This is especially important since the fiber bundles on the inside radius of the neutral axis of the cable have a shorter travel distance than fiber bundles on the outside of the neutral axis of the tube. Minimizing the strain in the loose-tube cable results in minimal mechanical and optical loss effects upon installation.
Unfortunately, with a loose-tube cable, the relative positions of the tubes as well as their relative spacing is not fixed and so is not maintained over the length of the cable. This becomes problematic during furcation, where the cable is cut and the fiber bundles accessed for processing, e.g., connectorization. In order to process the fiber bundles and the fibers carried therein, they need to be placed in their select order with uniform spacing, just like the ribbon cable ends. The conventional way to accomplish this ordering and spacing is manually, wherein a field worker handles each fiber bundle, identifies each fiber bundle (e.g., by its color) and places each fiber bundle in a fixture that establishes and maintains the correct relative positions. This process is time consuming and expensive.